CA1163091A

CA1163091A - Solutions for stabilizing thermoplastic polycarbonates

Info

Publication number: CA1163091A
Application number: CA000380651A
Authority: CA
Inventors: Erich Eimers; Rolf Dhein; Wolfgang Cohnen; Engelbert Kuhle; Gerhard Heywang
Original assignee: Bayer AG
Current assignee: Bayer AG
Priority date: 1980-07-12
Filing date: 1981-06-26
Publication date: 1984-03-06
Also published as: JPS6217619B2; JPS5749649A; EP0043998A2; EP0043998B1; DE3026503A1; DE3163198D1; EP0043998A3; US4367303A

Abstract

ABSTRACT OF THE DISCLOSURE
Certain solutions of phosphines in oxetane com-pounds impart oxidative stability to aromatic thermo-plastic polycarbonates in which such solutions are admixed.

Description

Mo-2222 LeA 20,430 SOLUTIONS FOR STABILIZING
THERMOPLASTIC POLYCARBONATES
FIELD OF THE INVENTION
The present invention relates to aromatic thermo-5 plastic polycarbonates and in particular to means to impart oxidative stability to said polycarbonates.
SUMMARY OF THE INVENTION
The present invention relates to solutions of phosphines of the formula I
(R)2PRl wherein R is an unsubstituted or substituted C6-C14-aryl radical and Rl = R or is an unsubstituted or substituted Cl-C18-alkyl radical, in oxetane compounds of the formula II

CH2 R2 ?\
~ \ / C ~ CH2 ~ - C ~ R3 II

20 wherein

2 1 16 alkyl and : R3 is either an n-valent radical of a C2-C8-alkane, which can also be substituted by OH groups~
and n ïs a number from 1 to 6, or R3 is a 2-valent radical of a cycloalkane and n is 2, or in oxetane compounds of the formula III

(~ \ ~ CH2 ~ Sl(R4~r III

Mo-2222 LeA 20,430 ~`~A~

~ 1 ~3~9 ~

wherein 2 1 16 lkyl, R4 is Cl-C4-alkyl, which can optionally be sub-stituted by cyano, carboxyl or acetoxy, or is allyl, C6-C14-aryl which is optionally substituted by alkyl, C7-C14-aralkyl or Cl-C4-alkoxy which can optionally be substituted by Cl-C4-alkoxy or allyloxy, m is an integer from 1 to 4 and r is an integer from 0 to 3, m + r always being 4.
The radicals R in the compounds of the formula I
can be either identical or different.
The particular components of the solutions according to the invention, that is to say the phosphines 15 and oxetane compounds, should have a boiling point of at least 200C; furthermore, the solutions according to the invention should have a melting point of at most 40C.
The mixing ratio of dissolved phosphine o~ the 20 formula I ~o the solvent containing oxetane groups, of formula II or III is between 3 and 10 oxetane group equivalents of the solvent containing oxetane groups per atom equivalent of phosphorus of the phosphine, in par-ticular between 4 and 8 oxetane group equivalents of the - 25 solvent containing oxetane groups per atom equivalent of phosphorus of the phosphine.
The present invention also relates to the use of the stabilizer solutions according to the invention for stabilizing polycarbonate.
The present invention also relates to a process for stabilizing thermoplastic polycarbonates, which is - characterized in that the stabilizer solutions according to the invention are added to the thermoplastic poly-Mo-2222 LeA 20,430

3~ ~

carbonate in a known manner during or after its prepara~
tion.
The present invention also relates to stabilized thermoplastic polycarbonates which have been stabilized S by the addition of the solutions according to the inven-tion in amounts of 0.02 to 1% by weight, relative to the total weight of thermoplastic polycarbonate and stabilizer solution.
The stabilizing operation according to the inven-tion on polycarbonates has the effect of stabllizingthem against the influence of heat and/or oxygen.
DESCRIPTION OF THE PRIOR ART
The stabilization of polycarbonates with phos-phines is known from Japanese Laid-Open Specification ~
72 22 088 of Mitsubishi Gas Kagaku (date of Application:
28.5.68, date of publication: 21.6.1972) and from DE-OS
(German Published Specification) 2,206,720. The latter literature reference also describes the stabilization of polycarbonates with mixtures of phosphines and epox-ide compounds.
The stabilization of polycarbonates with oxetanecompounds is also known (DE-OS (German Published Speci-fication) 2,658,8~9), as well as the stabili~ation of polycarbonates with mixtures of oxetane compcunds and phosphites (DE-OS (German Published Specification~
2,510,463 (LeA 16,231) and DE-OS (German Published Specification) 2,658,849).
According to British Patent Specification 1,141,869, silanes are suitable as trans-esterification catalysts which are used for the preparation of polycar-bonates by the me-lt trans-esterification process, and at the same time provide a stabili~ing effect and do not give rise to the discolorations and cloudiness of Mo-2222 LeA 20,430 0 ~ 1 the polycarbonate prepared, which some other trans-esterification catalysts cause. The silanes employed contain at most one alkoxysilané radical.
Combined stabili.zation with organic silicon 5 compounds and phosphites and, if appropriate, other stabilizers is described, for example, in ~E-OS (German Published Specification) 2,726,662, DE-OS (German Pub-lished Specification) 2,659,756, DE-OS (Gerrnan Published Specification) 2,741,064, DE-OS (German Published 10 Specification) 2,510,463 (LeA 16,231) and U.S. Patent Specification 4,138,379.
The stabilizer combination, claimed according to the invention, of phosphine and oxetane compound or silicon compound has not been described in any of the 15 l.iterature references mentioned.
The combination according to the invention is not obvious, for the following reasons:
As already mentioned, it was indeed known to use, on the one hand, phosphites containing oxetane yroups or 20 mixtures of oxetane-free phosphites and phosphorus-free oxetane compounds and, on the other hand, mixtures of phosphines and epoxy compounds as stabilizers .in poly-carbonates. However, from the advantageous effect of oxetane compounds on phosphites it could not have 25 been deduced that oxetane compounds would e~ert a similarly advantageous and synergistic effect on phos-phines, which have a completely different chemical ,structure and differ from the phosphites in that they contain no groups which can be split off by hydrolysis 30 and thus can be converted into phosphoric acids under the influence of hydrolytic processes. In contrast, if it is assumed that acid degradation products are also formed during the conversion of the phosphine in Mo-2222 LeA 20~430 ~ 1 ~30~ ~

the course of heat-ageing of the polycarbonate, it is again surprising that the polycarbonate which has been stabilized according to the invention have good hydro-lytlc stability, since, as is known, acid degradation products reduce the stability of the polycarbonate to hydrolysis.
As can be seen from the other examples given, neither phosphine by itsel~ nor a mixture of an ali-phatic phosphine and an oxetane compound, nor a mixture Of triphenylphosphine and an epoxide compound, have as good an action as that of the solutions claimed according to the invention. From this, it is evident that the action of the combination claimed according to the invention could be neither deduced nor predicted from the literature previously known or from the chemi-cal nature of the components of the solution.
DETAILED DESCRIPTION OF THE INVENTION
In the compounds of the formula I, the aryl radi-cals R can, for example, also be substituted by alkyl substituents, halogens or OH. The alkyl radicals Rl of the compounds of the formula I can be straight-chain or branched. They can be substituted, for example by OH, alkylcarboxy, cyano or phenyl.
Examples of phosphines of formula I which are suitable according -to the invention are: triphenyl-phosphine, diphenylbutylphosphine, diphenyl-octadecyl-phosphine, tris-p-tolyl-phosphine, tris-(p-nonyl-phenyl)-phosphine, tris-naphthylphosphine, diphenyl~
(hydroxymethyl) phosphine, diphenyl-acetoxymethyl-phosphine, diphenyl-(~-ethylcarboxy-ethyl) phosphine, tris-(p-chlorophenyl)-phosphine, tris-(p-fluorophenyl)-phosphine, diphenyl-benzyl-phosphine, diphenyl-~-cyano-ethyl-phosphine, diphenyl-(p-hydroxyphenyl)-phosphine, diphenyl-1,4-dihydroxy-phenyl-2-phosphine and phenyl-naphthyl-benzylphosphine.
Mo-2222 LeA 20,430 1 .1 &3~ 1 Either individual compounds or mixtures of the phosphines mentioned can be used.
Examples of oxetane compounds of formula II which are suitable accordin~ to the invention are: adipic 5 acid bis-3-ethyl-oxetanyl-3-methyl ester, adipic acid bis-3-amyl-oxetanyl-3-methyl ester, malonic acid bis-3-amyl-oxetanyl-3-methyl ester, azelaic acid bis-3-methyloxetanyl-3-methyl ester, sebacic acid bis-3-methyl-, oxetanyl-3-methyl ester, citric acid tris-3-methyl-lO oxetanyl-3-methyl ester, butane-1,2,3,4-tetracarboxylic acid tetrakis-3-ethyloxetanyl-3-methyl ester and cyclo-hexane-1,2-dicarboxylic acid bis-3-ethyloxetanyl-3-met~yl ester.
- Either individual compounds of formula'II or 15 mixtures of the compounds mentioned can be used. '' ; Exarnples of oxetane compounds of formula-III
which are suitable according to the,invention are methyl-tris-(3-ethyl-oxetanyl-3-methoxy)-silane, dimethyl-bis (3-amyl-oxetanyl-3-methoxy)-silane, bis-ethoxy-bis-(3-20 ethyloxetanyl-3-methoxy)-silane, phenyl-tris-(3-ethyl-oxetanyl-3-methoxy)-silane, benzyl-tris-(3-methyl-oxetanyl-t~methoxy)-silane, (~-~butoxyethoxy)-tris-(3-methyl-oxetanyl-~-methoxy)-silane, (3-allyloxy-ethoxy)-tris-(3-ethyl-oxetanyl-3-methoxy)-silane, diallyl-bis-25 (3-amyl-oxetanyl-3-methoxy)-silane, ~-cyanoethyl-tris-(3-propyl-oxetanyl-3-methoxy~-silane, ~-carboxyethyl-tris-(3-methyl-oxetanyl-3-methoxy)-silane, ~-phenyl-ethyl-tris-(3-ethyl-oxetanyl-3-methoxy)-silane and (3-acetoxy-propyl)-tris-(3-ethyloxetanyl-3-methoxy)-silane.
Either individual compounds of formula III or mixtures of the compounds mentioned can be used.
The compounds of the formulae I, II and III ~hich have been mentioned are known from the literature or Mo-2222 LeA 20,430 11 1 63~9~

can be prepared by processes which are known from the literature.
The thermoplastic polycarbonates to be stabilized according to the invention are the polycondensates 5 obtainable by reacting diphenols with phosgene or dies-ters of carhonic acid, dihydroxydiarylalkanes in which the aryl radicals in the o- and/or m-position relative to the hydroxyl group carry methyl groups or haloyen atoms are also suitable, in addition to unsubstituted lO dihydroxy~iarylalkanes. Branched polycarbonates are likewise suitable.
The polycarbonates to be stabilized have an average molecular weight of (Mw) of between 10,000 and 100,000, preferably between 20,000 and 40,000, deter- -15 mined by measurements of the relative viscosity in CH2C12 at 25C and at a concentration o~ 0.5~ by weight.
Suitable diphenols are, for example,- hydroquinone, resorcinol, 4,4'-dihydroxydiphenyl, bis-(hydroxy-phenyl)-alkanes, such as, ~or example, Cl-C8-alkylene- or C2-20 C8-alkylidene-bisphenols, bis-(hydroxyphenyl)-cyclo-alkanes, such as, for example, C5-Cl5-cycloalkylene- or C5-Cl5-cycloalkylidene-bisphenols, and bis-(hydroxy-phenyl) sulphides, ethers, ketones, sulphoxides or sulphones, furthermore, ~,~' bis-(hydroxy-phenyl)-25 diisopropylbenzene and the corresponding nuclear-alkylated or nuclear-halogenated compounds. Polycar-bonates based on 2,2-bis-(4-hydroxy-phenyl)-propane (bisphenol A), 2,2-bis-(4-hydroxy-3,5-dichlorophenyl)-propane (tetrachlorobisphenol A), 2,2-bis-(4-hydroxy-30 3,5-dibromophenyl)-propane (tetrabromobisphenol A), 2,2-bis-(4-hydroxy-3,5-dimethyl-phenyl)-propane (tetra-methylbisphenol A) or 1,1-bis-(4-hydroxyphenyl)-cyclohexane (bisphenol Z), and those based on trinuclear Mo-2222 LeA 20,430 ~ 3 6309 1 bisphenols, such as ~,~'-bis-(4-hydroxyphenyl)-p-diisopropylbenzene.
Other bisphenols which are suitable for the preparation of polycarbonates are described in U.S.
Patents 3,028,365; 2,999,835; 3,148,172; 2,970,131;
2,991,273; 3,271,367 and 2,999,846.
The stabilizer solutions accorcling to the inven-tion are prepared in a known manner by dissolving the phosphines in the oxetane compounds in the particular proportions, appropriately in the absence of atmos-pheric oxygen.
The stabilization, according to the invention, of the thermoplastic polycarbonates can be carrled out in any desired manner, and advantageously, for example, in the course of the preparation of the polycarbonate, and especially as a continuous procedure, since the stabilizers are liquid at low temperature. The stabilizer solution can be introduced continuously, through a suitable conveying pump, during the final phase of the preparation, in which the molten polycar-bonate is continuously freed from solvent in vacuo in a conveying screw. Furthermore, it is of course possible to stabilize the polycarbonate, for example by so-called tumbling, with the claimed solution after the preparation of the polycarbonate; this method is des-- cribed ln the examples o~ -this Application and is an incorporation method known from the literature.
The amounts of stabilizer to be employed are between 0.01 and 1% by weight, preferably between 0.02 and 0.5~ by weight and in partlcular between 0.05 and 0.2% by weight, in each case relative to the total weight of thermoplastic polycarbonate and stabili~er solution.

Mo-2222 ~eA 20,430 '~ 3 ~309 1 The pol~carbonates which have been stabilized according to the invention can also contain the known additives, such as, for example, fillers, dyestuffs, pigments and/or other stabilizers.
The thermoplastic polycarbonates which have been stabilized according to the invention can also be mixed with other thermoplastics in a known manner, for ex-ample with ABS polymers, polystyrenes, polyarylene-sulphones or polyalkylene terephthalates.
The polycarbonates which have been stabilized according to the invention are used, in particular, where the shaped articles produced are exposed to prolonged high temperatures, and in addition for all articles for which a high ligh-t transmission is required.
15 This applies, preferably to their use in the llght sector, for example for lamp coverings or glazing using polycarbonate sheets.
The parts mentioned in the examples are pàrts by weight.
20 Preparation of a polycarbonate 454 parts of 2,2-bis-(p-hydroxy-phenyl)-propane and 2.5 parts of p-tert.-butylphenol are suspended in 1.5 1 of water in a three-necked flask, provided with a stirrer and gas inlet tube, and the oxygen is then ,25 removed from the reaction mixture by passing nitrogen through the reaction mixture for 15 minutes, while stirring. 355 parts of 45~ strength sodium hydroxide solution and 1,000 parts of methylene chloride are then added. The mi~ture is cooled to 25C. 237 parts of 30 phosgene are added over a period of 120 minutes, while maintaining the above temperature by cooling.
An additional amount of 75 parts of 45~ strength sodium hydroxide solution is added after 15 to 30 minutes, or after the absorption of phosgene has started. 1.6 Mo-2222 LeA ~0,430 . , ~, 30~ :~

parts of triethylamine are added to -the resul-ting solu~
tion and the mixture is stirred for a further 15 minutes.
~ highly viscous solution is obtained, the viscosity of which is regulated by adding methylene chloride. The aqueous phase is separated off. The organic phase is washed with water until free from salts and alkali.
The polycarbonate is isolated from the washed solution and dried. The polycarbonate has a relative viscosity of 1.29 to 1.30, measured in a 0.5% strength solution in methylene chloride at 20C. This corresponds approximately to a molecular weight of 32,000. The polycarbonate thus obtained is extruded and granulated.
Preparation of stabilized polycarbonates The granular polycarbonate prepaxed according to the above description is mixed, by so-called tumbling, with the various phosphites or stabilizer solutions in the amounts given in the foIlowing table. The granules are then extruded to a strand at 300C in a mixing screw. This strand is again granulated, and the gran-ules are processed to standard test bars in an injection-molding machine at 330C.
The following stabilizers were employed:
I. Comparison experiments A) Tris-3-ethyl-oxetanyl-3-methyl phosphite B) Triphenylphosphine C) Tricyclohexylphosphine dissolved in adipic acid bis-3-ethyl-oxetanyl-3-methyl ester. Molar ratio of phosphine to oxetane compound = 1:3, corresponding to a ratio o~ P to oxetane group of 1:6 (the solution is solid at room temperature).
D) Triphenylphosphine dissolved in hexahydrophthalic acid bis-glycidyl ester. Molar ratio of 1:3, corres-ponding to a ratio of P to epoxide group of 1:6.

~o-2222 LeA 20,430 ~ :~ fi 30~ 1 -- 11 ~
II. According to the in~enti~n:
A) Triphenylphosphine dissolved in adipic acid bis-3-ethyloxetanyl-3-methyl ester. Molar ratio to o~etane compound = 1:3, corresponding to a ratio of P -to oxetane 5 group of l:G.
B) Triphenylphosphine dissolved in dimethyl-bis-3-ethyl-oxetanyl-3-methylsilane. Molar ratio of phosphine to oxetane compound - 1:3, corresponding to a ratio of P to oxetane group of 1:6.
The amount of stabilizer added is 0.1% by weight, relative to stabilized polycarbonate, in all the ex-amples.
Heat aging The test pieces produced in the manner described 15 above were heated at 140C in a drying cabinet. The light transmission was measured with -the aid of- a spectrophotometer. The particular drop in light trans-mission at 420 nm in the course of the heat treatment serves as a measure of the increasing browning of the 20 test pieces (see table).
Light transmission in %, measured in accordance with the method of DIN 5036, of PC bars at 420 nm in a cell thickness of 4 mm Stabilizer 0 hours 500 hours heating at 140C
25 I A 84 78.5 light transmission I C 81,5 (no brightening,effect) I D 80.5 (no brightening effect) 30 II B 83.5 82 ., .

Mo-2222 Le~ 20,430 .

Hydrolysis Test A number of shaped Makrolon~ articles which have been produced with and without stabilizers and have the dimensions 50 x 6 x 4 mm (so-called small standard bars) are stored in boiling distilled water in an electrically heated round-bottomed flask. After certain intervals of time, in each case lO bars are removed and their relative solution viscosity (in C~2Cl at 25C and at a concentra-tion of 0.5~ by weight) is measured. The resulting average values of the individual measurements on the lO bars are given in the following table.
~periment Before boiling Boiled for 500 hours ~;
relative relative viscosity viscosity PC, no stabilizer 1.296 1.275 0.020 I A 1.289 1.126 0.163 15 II A 1.297 1.278 0.019 It can be seen that the degradation in molecular weight during hydrolysis of the polycarbonate which has been stabilized according to the invention is no greater than in the case of unstabilized material, and that the degradation is significantly less than that o~ a polycarbonate stabilized with phosphite only.
:

Mo-2222 LeA 20,430 ..`~
.~

.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows.
l. A solution comprising at least one phosphine of the general formula (R)2P-Rl I
wherein R and R1 independently denote an unsubstituted or substituted C6 to Cl4 aryl radical and Rl may additionally denote an unsubstituted or substituted Ci to C18 alkyl radical in at least one oxetane compound of the general formula II

wherein R2 denotes a Cl to C16 alkyl radical and R3 is either an n-valent radical of a C2 to C8 alkane, which may be substituted by at least one OH group and n is 1, 2, 3, 4, 5, or 6 or R3 is a divalent radical of a cycloalkane and n is 2, or in at least one oxetane compound of the general formula III

wherein R2 denotes a Cl to Cl6 alkyl radical, R4 denotes a Cl to C4 alkyl radical which.may be substituted by cyano, carboxyl, or acetoxy, an Mo-2222 LeA 20,430 allyl radical, a C6 to C14 aryl radical which may be substituted by alkyl, or a C7 to C14 aralkyl or Cl to C4 alkoxy radical which may be substituted by Cl to C4 alkoxy or allyloxy, m is 1, 2, 3, or 4 and r is 0, 1, 2 or 3 with the proviso that m + r equal 4, in which the mixing ratio of dissolved phosphine of the formula I to solvent, containing oxetane groups, of the formula II or III is between 3 and 10 oxetane group equivalents of the solvent containing oxetane groups per atom equivalent of phosphorus of the phosphine.
2. The solution of Claim 1, wherein said mixing ratio is between 4 and 8 oxetane group equivalents of the solvent containing oxetane groups per atom equiva-lent of phosphorus of the phosphine..
3. The solution of Claim l wherein said R is a C6 to C14 aryl, substituted by a member selected from the group consisting of alkyl, halogen and OH radicals.
4. The solution of Claim 1 wherein said Rl is a straight chain Cl to C18 alkyl.
5. The solution of Claim 1 wherein said Rl is a branched Cl to C18alkyl.
6. rrhe solution of Claim 1 or 4 or 5 wherein said Rl is substituted by a member selected from the group consisting of OH, alkyl carboxy, cyano or phenyl radicals.
7. A process for stabilizing a thermoplastic polycarbonate comprising adding thereto a stabilizer solution comprising at least one phosphine of the general formula (R)2P-R1 Mo-2222 wherein R and Rl independently denote an unsubstituted or substituted C6 to C14 aryl radical and Rl may additionally denote an unsubstituted or substituted Cl to C18 alkyI radical in at least one oxetane compound of the general formula II
wherein R2 denotes a Cl to C16 alkyl radical and R3 is either an n-valent radical of a C2 to C8 alkane, which may be substituted by at least one OH group and n is 1, 2, 3, 4, 5, or 6 or R3 is a divalent radical of a cycloalkane and n is 2, or in at least one oxetane compound of the general formula III

wherein R2 denotes a Cl to C16 alkyl radical, R4 denotes a C1 to C4 alkyl radical which may be substituted by cyano, carboxyl or acetoxy, an allyl radical, a C6 to C14 aryl radical which may be substituted by alkyl, or a C7 to C14 aralkyl or Cl to C4 alkoxy radical which may be substitut-ed by Cl to C4 alkoxy or allyloxy, Mo-2222 LeA 20,430 m is 1, 2, 3, or 4 and r is 0, 1, 2 or 3 with the proviso that m + r equal 4, in which the mixing ratio of dissolved phosphine of the formula I to solvent, containing oxetane groups, of the formula II or III is between 3 and 10 oxetane group equivalents of the solvent containing oxetane groups per atom equivalent of phosphorus of the phosphine said solution being added to said polycarbonate either during or after its preparation.
8. The process of Claim 7 wherein said mixing ratio is between 4 and 8 oxetane group equivalents of the solvent containing oxetane groups per atom equivalent of phosphorus of the phosphine.
9. The process of Claim 7 wherein said Rl is is a C6 to C14 aryl, substituted by a member selected from the group consisting of alkyl, halogen and OH
radicals.
10. The process of Claim 7 wherein said Rl is a straight chain Cl to C18 alkyl.
11. The process of Claim 7 wherein said Rl is a branched Cl to C18 alkyl.
12. The process of Claim 7 or 10 or 11 wherein said Rl is substituted by a member selected from the group consisting of OH, alkyl carboxy, cyano or phenyl radicals.
13. The process of Claim 11 wherein said stabiliz-er solution is added in an amount of 0.01 to 1% by weight, relative to the total weight of thermoplastic polycarbonate and stabilizer solution.
14. The process of Claim 11 wherein said stabiliz-ersolution is added in an amount of 0.05 to 0.2% by weight, relative to the total weight of thermoplastic polycarbonate and stabilizer solution.
Mo-2222 LeA 20,430
15. A stabilized thermoplastic polycarbonate obtained by a process comprising adding to a thermo-plastic polycarbonate a stabilizer solution which com-prises at least one phosphine of the general formula (R)2P-R1 I
wherein R and Rl independently denote an unsubstituted or substituted C6 to C14 aryl radical and Rl may additionally denote an unsubstituted or substituted Cl to C18 alkyl radical in at least one oxetane compound of the general formula II

wherein R2 denotes a Cl to C6 alkyl radical and R3 is either an n-valent radical of a C2 to C8 alkane, which may be substituted by at least one OH group and N is 1, 2, 3, 4, 5, or 6 or R3 is a divalent radical of a cycloalkane and n is 2, or in at least one oxetane compound of the general formula III
Mo-2222 LeA 20,430 wherein R2 denotes a Cl to C16 alkyl radical, R4 denotes a Cl to C4 alkyl radical which may be substituted by cyano, carboxyl or acetoxy, an allyl radical, a C6 to C14 aryl radical which may be substituted by alkyl, or a C7 to C14 aralkyl or Cl to C4 alkoxy radical which may be substituted by Cl to C4 alkoxy or allyloxy, m is 1, 2, 3, or 4 and r is 0, 1, 2, or 3 with the proviso that m + r equal 4, in which the mixing ratio of dissolved phosphine of the formula I to solvent, containing oxetane groups, of the formula II or III is between 3 and 10 oxetane group equivalents of the solvents containing oxetane groups per atom equivalent of phosphorus of the phosphine said solution being added to said polycarbonate either during or after its preparation.
16. The solution of Claim 1 wherein R and Rl are unsubstituted C6-C14 aryl radicals and Rl additionally is an unsubstituted Cl-C18 alkyl radical.
17. The process of Claim 7 wherein R and R1 are unsubstituted C6-C14 aryl radicals and Rl is additionally an unsubstituted C1-C18 alkyl radical.
18. The stabilized thermoplastic polycarbonate of Claim 15 wherein R and Rl are substituted C6-C14 aryl radicals and Rl is additionally an unsubstituted Cl-C18 alkyl radical.
Mo-2222 LeA 20,430